Hi, I would like to get involved in a project.
But there is a problem. I do not know how.
Every project I would like to try is way too hard to write into and too complicated at all.
I am not a real beginner, I think I could make something, but question is what ?

Helping with Documentation is almost always the best place to start contributing to a project. Almost every one needs help with documentation, and in doing so you will develop a much deeper understanding for the product.

Then you can start contributing to the code base if you feel comfortable enough with the product and process.

I guess first step would be to identify which language or what type of projects you want to be involved in.

Then make a conscious effort to learn the language. Read some books. Develop sample programs.

Once you are comfortable with the language you may want to start with an open source project by fixing some bugs. Once you feel you are confident enough and understand the project you may contribute more.

Most open source programmers, I think, start by solving a problem that they have or by helping improve something they would like improved in some project they use and/or like.

Some times there are simple things that can be done, just to start - like writing a plugin for a CMS that you use - like Wordpress, or Joomla, or anyother. Or, maybe, you find something that you think that could work better in a different way, or something that would make some project more useful.

When you find something that you'ld like improved, try to improve it youself, and send the author/maintainer a patch for improvement or the correction.

But, in the end, I don't believe there is any final formula - just scratch your itch.